Solvent fractionation of gasoline



March 9, 1937. SIMONS ET 2,073,517

SOLVENT FRACTIONATION 0F GASOLINE Filed June 14, 19.53 2 Sheets-Sheet l ww\ Iv sak 42m mm Mm mm oLowm mom b w bm March 9, 1937. o'. FlTZ suvloNs ET AL 2,073,517 SOLVENT FRACTIONATION OF GASOLINE I 2 Sheets-Sheet 2 Filed June 14, 1933 VON QQN NR mn @HQQE T W o v Wm m6 m m wuw m BY 5% BMSi ATTORNEY Tab Patented Mar. 9, 1937 UNITED STATES PATENT oFFlfcE Hammond,

Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application June 14, 1933, Serial No. 675,748

6 Claims. (01. 196-13) This invention relates to the preparation of high antiknock gasoline or motor fuels, and it pertains more particularly to gthe preparation of high antiknock gasoline from petroleum naphand it has been found that certain classes of these hydrocarbons have high octane numbers, or in other words, retard the detonation characteristics of gasolines and motor fuels. The fraction of compounds is called the anti-detonating fraction or anti-detonating constituents. The saturated hydrocarbons, and particularly the straight chain compounds present in these naphthas, do not possess the property of suppressing the detonating characteristics of motor fuels. This fraction of compounds is called the detonating fraction or detonating constituents. The effectiveness of a material or compound for retarding or suppressing the detonating characteristics of a motor fuel is expressed-in terms of itsoctane number, which method of evaluation is described in The National Petroleum News, June, 1930; page 35. We have found that the antiknock fraction of hydrocarbons, or fraction'oi hydrocarbons having a high octane number, present in petroleum naphthas can be extracted therefrom by the use of a mixture of S02 and low-boiling aliphatic hydrocarbons.

The object of our invention, therefore, is to extract the fraction of antiknock compounds present in petroleum naphtha from the other hydrocarbons and compounds present therein.

Fig. 1 is a diagrammatic flow plan of a process used to extract the high antiknock fraction of compounds from petroleum naphthas and the like.

Fig. 2 is a diagrammatic flow plan of a process used in the countercurrent extraction of the high antiknock fractions of compounds from low antiknock motor fuels.

We have discovered that the low-boiling saturated aliphatic hydrocarbons, preferably having a straight chain structure, such as ethane, propane, butane, and normal hexane, when mixed with liquid SO2,.greatly increase the selectivity of the S02 when used to extract the antiknock valved by-pass 2| is provided around the comfraction of hydrocarbons from petroleum naphhas. When $02 per se is used to extract a petroleum naphtha of about 60 octane number, the octane number of the extract will vary from 60 to 80 whereas the presence of a relatively 5 small amount of low-boiling parafiin hydrocarbons in the naphtha or $02 will increase the octane number of the extract to at least 100 or above. The low-boiling aliphatic hydrocarbons or mixture of saturated straight chain hydrocarbons to be used in combination with the S02 should boil below the initial boiling point of the petroleum naphtha to be extracted. We may employ the commercial grades of hydrocarbons which contain mixtures of aliphatic hydrocarbons and in some cases, such as plant propane, some" olefins may be present, but we prefer to use the grade of hydrocarbon that contains from about 70 to 100% of the hydrocarbon under consideration. We will describe one preferred embodiment of our process with reference to Fig. 1, in which a continuous one-step extraction process is used. Heavy petroleum naphtha having an initial boiling point of about 250 R, an end point of about 400 F. and an octane number of 62 is passed by the line In into the mixer II where it is throughly contacted with liquid propane which is pumped from the storage tank l2 by the pump l3 and conduit It. The mixture of naphtha and propane passes from the mixer ll through the valved conduit IE to the chiller I 6 where a portion of the propane is flashed by a pressure release device ll in order to cool the naphtha to 'a temperature belowO" F. and preferably below -10 F. The evaporated propane leaves the chiller through the conduit l8 and passes to i the compressor l 9 and condenser 20 and returned to the storage tank [2 in the liquid form. A 40 pressor so that the gaseouspropane can be passed directly to the condenser 20 if desired.

In this particular example, the naphtha in chiller It was cooled to 40 F. However, temperatures as low as and F. or lower may be used. The amount of propane added to the naphtha in mixer l I should be adjusted so that after the flashing operation in the cooler Hi there will be from 0.2 to 3 volumes of liquid propane for each volume of naphtha. In this 50 particular example we used one volume of liquid propane for each volume of naphtha.

The mixture of propane and naphtha in th chiller I6 is then passed through conduit 22 by the pump 23 and introduced into the lower part of the extractor or tower 24. A perforated conduit 25 or plurality of perforated pipes may be used to obtain equal distribution of the mixture in the lower part of the extractor.

Liquid sulfur dioxide, which has been cooled to about the same temperature of the naphthapropane mixture (40- F.) is introduced or sprayed into the top part of the extractor 24 by the perforated conduit 26. The cold liquid sulfur dioxide passes down through the tower or extractor, countercurrent to the rising mixture of propane and naphtha. Baflle plates or other suitable means may be used to insure thorough contact between the naphtha and solvents in the extractor 24. The amount of S02 added to the top of the tower or extractor 24 may vary from 0.5 to 3 volumes for each volume of naphtha. In this particular example two volumes of S02 and one volume of propane were present in the extractor 24 for each volume of naphtha. It should be understood, however, that our process can be performed with varying proportions of the sulfur dioxide and low-boiling aliphatic hydrocarbons.

The raffinate and the major part of the propane rise to the top of the extractor 24 and are withdrawn therefrom by the pump 21 and pass to thestripper 28. A small amount of S02 will also be present in the rafilnate. A steam coil 29 or some suitable heating element is placed in the lower part of the stripper to distil the propane and the small amount of S02 from the raflinate. Suitable baille plates 30 are placed in the stripper to aid the separation of the raffinate from the vaporized propane. Also a reflux coil may be placed in the top part of the stripper to further aid'the separation of the propane from the naphtha. The vaporized propane with some SO: which is present in the raflinate layer is passed from the top part of the stripper through the conduit 3| to the compressor 9 and condenser 20 where it is condensed and passed to the propane storage tank |2 for re-use. If desired, the stripper 28 may be operated under pressure, for example, 125 pounds, in which case the propane removed from the stripper may be by-passed through the valved conduit 2| and passed directly to the condenser 20. The small amount of S02 present in the propane does not interfere with subsequent use of the propane. However, if desired, this S02 may be removed by washing the gaseous propane with an alkaline solution, or by fractionation. The extracted naphtha, or rafllnate, which is free of the solvent, is removed from the bottom part of the stripper 28 through the conduit, 32.

The sulfur dioxide and dissolved fraction of antiknock hydrocarbons pass from the lower part of the extractor 24 by the conduit 33 and pump 34 and enter the stripper 35. A certain amount of propane will also be present in this extract.

A closed steam coil 36 or some suitable heating means is placed in the bottom part of the stripper to distil the S02 from the extract, or high anti knock fraction of compoundsyremoved from the naphtha. Baflles 31 or other fractionating means may be used to aid the separation of the S02 from the antiknock fraction of hydrocarbons. Also, reflux coils may be used in the top part of the stripper to further aid this fractionation. The distilled S02 is removed from the stripper by the conduit 38 and passes to the compressor 39 and condenser 40 where it is again liquefied and stored in tank 4| for reuse. As stated hereinbefore, the liquid S02 is cooled to the extraction temperature before being introduced into the extractor 24. The cooling of the S02 may be effected by one'of several methods such as by contacting the S02 with pipes which are cooled with brine or some suitable refrigerant, but we prefer to pass the liquid sulfur dioxide through the valved conduit 42 and pump 43 to the cooler 44 where propane and a part of the S02 are flashed by a pressure reducing valve 45 disposed on the top part of the cooler. The vaporized sulfur dioxide passes through the conduit 46 to the compressor 39 and condenser 40 where it is liquefied for reuse; We prefer, however, to obtain the necessary cooling by evaporating propane which may be done by introducing liquid from tank I2 by line 43a into cooler 44. In this case we prefer to pass the vapors to line 3| which may be done by closing valve 46a and opening valve 46b. Compressor 460 in the line 46d may 'be used to urge the vapors against any back pressure existing in line 3|. A valved by-pass 41 may be placed around the compressor 39 so that the gaseous sulfur dioxide can be passed directly to the condenser 40. The cold liquid sulfur dioxide in the cooler tank 44 is now ready to be passed by pump 44a to the top part of the extractor 24.

The extract, or fraction of high antiknock hydrocarbons, is removed from the bottom of the stripper 35 through the conduit 48. This fraction of hydrocarbons may now be added to gasoline or a motor fuel to increase the octane number or antiknock value of said fuel. Also, organic reducing agents or antioxidants such as phenols, polyhydroxy benzene compounds, catvary overv a wide range, but sufllcient pressure should be maintained so that the solvents will always be in the liquid phase during extraction. Pressure, per se, has practically 'no eflect upon the yields obtained.

The following table shows the results obtained in a batch extraction process when used to extract a heavy naphtha having an octane number of 62,--

Table I Volume Railinata Extract ratio of Extraction naphtha tempera- 801 and ture Yield Octane Yield OctaneNo. propane No. (CIR-R) Percent Percent 1:2:1 ill I. 77.6 46 22 5 1:3:0. 6-.-; l0 F. 40. 5 86, 5 -1:6:0.4 40 4410 97 65 more conduits similar to 62 may be installed at Other saturated aliphatic hydrocarbons maybe used in the place of propane. The following table represents the results obtained when other hydrocarbons are used:

Table II Votlium? vriliumte Exitrac- Extmct re 0 0 re 0 o t on Example naphtha hydrocarbon temper- 0 ta and S02 used ature Yield 1:2 1 hexane -40 F. 115 1:2 1 hexane 90 23 115 1:2 0.3 propane".... -40 31 105 1:5 0.4 propanem. --40 40 97 1:3 3 hexane +5 20 95 1:2 29 87 1:4 40. 6 84 1:2 0.3 butane 41v 81.5 1:2 0.3 propane 40 30.5 105 (plant).

Note.The hexane used in this work was a commercial fraction of petroleum with the following distillation characteristics: Initialabove 100 F.Maximumbelow 180 F.

"Note-The propane employed in these tests consisted of 97% of propane and the rest, other light, saturated hydrocarbons, with the exception of that used in Example 9 which contained about 30% of oleflns.

figure 2 represents'a modified form of our invention in which a heavy petroleum naphtha is extracted concurrently in a three stage batch countercurrent process with a mixture of S02 and a low-boiling aliphatic hydrocarbon. In this particular example we'used a mixture of S02 and propane as the solvent. The naphtha to be extracted had an initial boiling point of about 270 F. andan end point of about 430 F. However, our invention is applicable to any heavy petroor end boiling point above or below that of the above naphtha. The initial and end boiling point of the heavy naphtha is not a limitation upon the operativeness of our invention, so long as the initial boiling point of the heavy naphtha is at least 40 F. above the boiling point of the aliphatic hydrocarbon used in combination with the S02.

Liquid propane and S02 are introduced into the storage tank through the valved conduit 6!. The mixture of solvents is then passed through the valved conduit 62 to the cooler or tank 63 where a portion of the S02 and/or propane is flashed by the valve 64. At temperatures above 0 F. to 5 F., the propane and $02 in tank 60 are miscible while below these temperatures the two liquids separate. The lower layer ispredominantly S02 and the upper layer is predominantly propane. In case of stratification two or difi'erent levels on the tank 60. The gaseous S02 and propane pass through'the conduit 65 to the compressor 66 and condenser 61, where they are condensed, and thence flow back to the storage tank 60; A valved by-pass 68 is placed around the compressor 66 so that the vaporized propane and S02 can be passed directly to the condenser 61 if desired. By the above flashing operation, the mixture of S02 and propane in the cooler 63 may be cooled to the temperature at which the leum naphtha which has an initial boiling point extraction is to be performed. Generally, the mixture is cooled to atemperature below '0 F. and preferably below -10 F. In this particular example, we use a temperature of .-40 F. At temperatures below 0 F. the propane and S02, in

lects in the bottom part of the container. This condition is also true with S02-butane and S02- hexane, and the like. Consequently, if a mixture of S02 and propane is to be withdrawn from thecooler 63, stratify and most of the S02 colthe cooler 63, provisions must be made to withdraw the S02 from the bottom part of the container 63 and propane from the top part of said container.

The cold S02 and propane are withdrawn from the cooler 63 through the valved conduits 69 and GQarespectively by pump and forced to the mixer 10 where the raflinate from settler B is thoroughly mixed with the fresh propane and S02. Conduit 69a is attached to the cooler 63 above the level of the S02 layer in order that propane can be withdrawn from the cooler 63. The proof the propane and/or S02 can be flashed to further cool the naphtha and solvents, in said settler. The flashed propane and S02 pass through the manifold 12 to the compressor 13 and condenser'fi'l, where they are liquefied, and

thence to the storage tank 60.

The extract and S02, together with a small amount of propane are withdrawn from the bottom part of the settler C by the pump I4 and conduit 15, and forced into the mixer 16 where they are thoroughly mixed with the raffinate from settler A. As explained hereinbefore, the major part of the propane dissolves in the railinate and does not remain in the extract fraction. Also, additional solvent, comprising propane and/or a small amount of S02 is added to the mixer I6 from the tank or cooler 63 by the valved conduits/l1, l8 and Illa and pump Tia. However, if it is desired to add only propane to the mixer 10, the valve in conduit 10a is opened. Additional S0 may be added to the mixer 16 by lines IT and 18 and pump Tia. The valves in conduits l8 and 18a are adjustable and are used to control the proportions of propane and S02 removed from the cooler 63. The mixture of naphtha, S02 and propane passes from the mixer 16 through the conduit 10 to the settler B where the S02 and extract separate from the A valve or pressure reducing means is placed on the top part-of the settler B so that a portion of the propane and/or S02 can be flashed in order to maintain the desired temperature in the settler B. The flashed S02 and propane are passed to the manifold 12, liquefied by the compressor 13 and condenser 61 and then returned to'the storage tank 60. The raffinate from settler B is withdrawn through conduit 8| by pump 81a to the mixer 10. I

The extract and S02, together with a small amount of propane, are withdrawn from the lower part of the settler B and passed by the changer 85 is cooled in a manner to be described hereinafter. The cold naphtha then passes through the conduit 81 to the mixer 84 where it is thoroughly mixed with the extract and S02 from settler B. Also, additional solvent, comprising propane and/or S02 is added to the mixer 84 from the valved conduit 88 which is connected to the propane-S02 cooler 63, the valves in conduits I8 and 18a being used to control the pro- 4 portion of S02 and propane. The mixture of the naphtha, propane and SO: passes from the mixer 84 by the conduit 89 to the settler A. A pressure reducing valve 90 is placed on the top part of the settler A so that a portion of the S02 and/or propane can be flashed in order to effect further cooling of the naphtha in the settler A i if desired. The raffinate from the top part of settler A is then forced through conduit 9| by pump 9Ia to the mixer I6.

The S02 and extract, or $02 and antiknock fraction of hydrocarbons, in settler A, are withdrawn therefrom by the conduit 92 and pump 93 and passed through the exchanger 85. The incoming naphtha, or unextracted heavy naphtha, is passed in heat exchange relation in the exchanger 85 so as to utilize the low temperature of the S02 and extract. The extract, comprising the S02 and antiknock fraction of hydrocarbons, is then passed by the valved conduits 94 and 95 to the stripper 96. If desired, the extract and solvent from settler A may be bypassed around the heat exchanger 85 by the valved conduit 91.

A closed steamcoil 98 is placed in the lower part of the-stripper 96 in order to distil the S02 and propane from the antiknock fraction of hydrocarbons removed from the naphtha. The vaporized S02 and small amount of propane pass through the conduit 99 to the compressor I00, conduit ml and condenser 61, and thence to the storage tank 60. If desired, the vaporized 802 and propane maybe by-passed around thecompressor I00 by the valved conduit I02. The extract, or antiknock fraction of hydrocarbons removed from the naphtha, is withdrawn from the bottom part of the stripper 96 by the valved conduit I03. This extract is now ready to be added to gasoline or motor fuels in order to improve the antiknock value or octane number of said motor fuels. If desired, the extract may be given the conventional refining treatments such as washing with alkali, water and/or sulfuric acid. The alkali and/or water wash will remove the last traces of S02, whereas the acid will remove the sulfur compounds therefrom. The raiiinate may also be given further refining treatment, such as an acid treatment. Preferably, this acid treatment should be performed in the cold. This fraction of antiknock compoundsmay be stabilized with antioxidants such as phenols, hydroquinone, pyrogallol, wood tar creosote, aminophenols, para-aminophenol, para-methyl aminophenol, phenyl aminophenol, benzyl ami-' nophenol, anthracene, alpha naphthol, tributylamine and the like.

The rafiinate from the top part of settler C is withdrawn through the conduit I04 by the pump I05 and introduced into the stripper I06. A closed steam 0011' I0! is placed in the lower part of the stripper in order to distil the propane and small amount of $02 from the raftlnate. The distilled solvents are passed through the conduit I08 to the compressor 66 and condenser 61 where they are liquefied and returned to the storage tank 60. The rafllnate, free from the solvents, is withdrawn from the bottom part of the stripper I00 throughthe valved conduit I09.

The motor fuel to be extracted by the herein described process may be prepared by first fractionating a cracked motor fuel distillate into a low boiling and a high boiling fraction and then extracting the high boiling; fraction with the combination of solvents herein disclosed. The high antiknock hydrocarbons removed from the high boiling fraction may be combined with the lowboiling fraction of gasoline prepared by the fractionation step to form a high antiknock gasoline.

In the processes illustrated by Figs. 1 and 2 we have used only one stage of stripping, but in general multi-stage stripping is preferred. The first stripping is performed at about the same pressure used to maintain the solvents in a liquid phase and consequently the solvents removed may be condensed without further compression. The second stage should be performed at a lower pressure and preferably by scrubbing with propane.

The process described above and illustrated by Fig. 2 is very flexible and can be operated under varying conditions. The temperature maintained in the system may range from 10 F. to as low as F. In performing the process, the temperature in each of the settlers A, B, and C may be maintained at about 40" F.,' or the temperature may be progressively decreased, for example,

settler A may be maintained at about 40" F.; in

settler B at about -50 F. and settler C at about 60 F. Temperatures above or below those set forth above may be used. Also, the temperature used in the three stages may be progressively increased from settler A to settler C and this is the preferred method of operation. For example, the temperature maintained in settler A may be 60 F., settler B 40 F., and settler C 20 F. By progressively increasing the temperature in the three stages, the miscibility of the SOs-propane solvent increases, and consequently more of the naphtha is dissolved in the extract. The following table gives the general range of combinations of temperatures that may be employed in the three stage' extraction.

If hydrocarbons heavier than propane are used, temperatures may all be higher and, conversely, if ethane is used, the temperatures will be lower.

The ratio of solvent to heavy naphtha used in the three stages may be constant or the proportions of solvent and heavy naphtha may be progressively increased or decreased. For example, two volumes of S02 and one volume of propane may be used for each volume of heavy naphtha in each of the three stages. As an example of varying proportions, 2.5 volumes of SO: and 1.5 volumes of propane may be used in extractor C for each volume of heavy naphtha; 2 volumes of S02 and 1 volume of propane may be used In extractor B for each volume of heavy naphtha; and 1.5 volumes of SO: and .8 volume of propane may be used in extractor A for each volume of heavy naphtha. The following table gives the Table IV Stage A- Stage B- Stage C- volume ratio: volume ratio: volume ratio Example SOg-pro- SO pro- SOT-propane-heavy paneheavy pane-heavy naphtha naphtha naphtha 2:1:1 2:1:1 2:1 1 2:1:1 2.5:1:1 3:1 1 I 2:0.5z1 2:111 2:1.5 1 2:0.5:1 2. 5:1:1 3:1.5 1 2.5:lzl 2:1.5:1 2:1 1

The temperatures employed when the above volume ratios of solvent are used may conform to any of the temperature conditions set forth in Table 131. One skilled in the art can easily 20 operate the process illustrated in Fi 2 S0 that the solvent ratios and temperature conditions will conform to any of the conditions set forth in Tables HI and IV. In one mode of operation, the

volume ratio of solvent to heavy naphtha may be 25 maintained or adjusted as follows: The cold liquid propane from the cooler 63 may be passed through the conduits 18a and 88 to the mixer 84 where the untreated heavy naphtha enters the extracting system. The cold liquid S02 inthe lower part of the cooler 63 may be passed through the conduit 69 to the mixer lll.- Since most of the propane passes into the rafiinate, th'e raflinate from settler B will contain sufiicient propane to enhance the effectiveness of the $02. The solvre ating the amount of propane introduced into the mixer 86 and regulating the amount. of S02 added to mixer l0 and recycled to settlers ent contained in the extract removed from the- 453 and C, it is possible to maintain any desired ratio of solvent within the various stages of the process. Another method for varying or controlling the ratio of S02, propane and naphtha in the three stages, is by adding propane and/or 50 S02 from the cooler 63 to the mixers'llL'lG and While we have described our process by using three stages of extraction, it should be understood that any number of stages may be'em- 55 ployed, however, we have found that from three to five stages give high yields of high octane number extracts. By the three stage extraction, a 25 to 50% yield of 100 to 115 octane number extract can be obtained from heavy naphtha hav- 60 ing a 62 octane number. Instead of liquid S02 as the selective solvent we may use other solvents to selectively dissolve high octane constituents, and particularly unsaturated olefinic hydrocarbons, from hydrocarbon mixtures. As examples of such solvents we may use acetone, methyl, ethyl and lsopropyl alcohols, beta beta dichlor diethyl ether, methyl ethyl ketone, carbon dioxide and mixtures of carbon dioxide and S02, chlorhydrin and epichlor-hydrin, dichlorhydrin, 70 phthalic anhydride, acetic anhydride and other anhydrides, organic acids, alcohols, ketones and other organic chloro-oxygen compounds. Obviously, the best temperatures required for extraction of gasoline with these various solvents will 75 be different for each solvent as will also be the proportions of solvent to naphtha and unsaturated aliphatic hydrocarbons. The use of all solvents, however, has the common feature that a saturated aliphatic hydrocarbon, preferably of normal structure, is employed in co-operation with a solvent which selectively dissolves olefins and high octane constituents from mixtures with low octane value hydrocarbons. I

In place of the saturated normal aliphatic hydrocarbons. we may employ hydrocarbons obtainedirom the rafilinate rejected in the selective extraction process itself. Thus, we may fractionate a cracked hydrocarbon distillate into high boiling and low boiling constituents and we may extract the low boiling constituents with liquid sulfur dioxide with or without the presence of liquid propane for example and obtain from this extraction a low boiling railinate fraction insoluble in the sulfur dioxide. We may then use this raflinate fraction in lieu of propane or other low boiling normal aliphatic hydrocarbons in the extraction of heavy naphtha with sulfur dioxide.

In this case, as in the case of propane, it will be found that a large proportion of the low boiling rafiinate fraction will be separated with the rafflnate from the heavy naphtha. However, that portion which remains dissolved in the heavy' naphtha extract may be readily separated therefrom by distillation, thus producing a high octane heavy naphtha extract in the extraction of light naphtha, in which case the heavy raillnate serves to collect the undesirable low octane constituents from the light naphtha and remove them in the raiitinate. Any heavy ramnate which dissolves in the extract layer may be readily separated therefrom by distillation and thus will not contaminate the desired product. This is not the preferred method, however, but it is more effective to extract the heavy naphtha with the aid of rafiflnate from light naphtha rather than the reverse.

In any of the foregoing operations we may subiect the rafhnate to a suitable pyrolytic reform-= ing operation whereby unsaturated and high octane hydrocarbons are produced therefrom. The product of such a reforming operation may be used directly as a motor fuel or it may be further extracted, either alone or in conjunction with cracked gasoline obtained from other sources.

The reason for the enhanced results obtained in the extraction of cracked gasoline and unsaturated petroleum distillates by the simultaneous use of a normal parafiin hydrocarbon and a selective solvent such as liquid sulfur dioxide is not understood. It would be expected that the" planation thereof it is thought that possibly the by the added third ingredient, thus forcing a larger proportion of the undesired low octane saturated constituents into the rafiinate layer.

The third ingredient, being selected of diflerent boiling point than the hydrocarbon fraction undergoing extraction, it is then possible to separate it by distillation from the final extract product. 5 Although the third ingredient may be selected either higher boiling or lower boiling than the material undergoing extraction, it is preferable to employ the latter condition partly for the greater ease of subsequent separation by distillation and partly because the lower boiling-lower molecular weight hydrocarbons appear to be more effective. Although applicants have advanced this theory for their process they do not wish in any way to be confined thereto and have set forth the scope of their invention by the following claims.

We claim:

1. In the process of separating cracked pe-.

troleum naphtha containing relatively high antiknock components and relatively low antiknock components into phases, respectively, which contain more of the relatively high antiknock components and more of the relatively low antiknock components than the originalcrackednaphtha, the steps comprising mixing the cracked naphtha at a. temperature below 5 F. with an admixture of liquid sulfur dioxide and liquid propane, passing the resulting admixture into a settling zone to permit phase separation wherein the relatively high antiknock components together with a substantial portion of the liquid sulfur dioxide collect in the lower part of the settling zone and the relatively low antiknock components together with a substantial portion of the propane collect in the upper part of the settling zone, removing said phases from said zone, mixing the phase removed from the lower part of the separating zone at a temperature below 5 F. with cracked naphtha containing dissolved propane, passing the resulting admixture into a second settling zone and again 40 permitting phase separation as in the first settling zone, removing from the lower part of the second settling zone the phase containing the relatively high antiknock components together with liquid sulfur dioxide and separating the liquid sulfur dioxide from the relatively high antiknock components.

2. In the process of separating cracked petroleum naphtha containing relatively high antiknock components and relatively low antiknock components into phases, respectively, which contain more of the relatively high antiknock components and more of the relatively low antiknock components than the original cracked naphtha, the steps comprising mixing the cracked naphtha at a temperature within the'range of to +5 F. with an admixture of liquid sulfur dioxide and liquid propane, passing the resulting admixture into a settling zone to permit phase separation wherein the relatively high antiknock components together with a substantial portion of the liquid sulfur dioxide collect in the lower part of the settling zone and the relatively low antiknock components together with a substantial portion of the propane collect in the upper part of the settling zone, removing said phases from said zone, mixing the phase removed from the lower part of the separating zone at a temperature within the range of -40 to F. with cracked naphtha containing dissolved propane, passing the resulting admixture into a second settling zone and again permitting phase separation as in the first settling zone, removing from the lower part of the second settling zone the phase containing the relatively high antiknock components 75 together with liquid sulfur dioxide and separating the liquid sulfur dioxide from the relatively high antiknock components. 7

3. The method of separating high antiknock components from cracked hydrocarbon distillates which comprises, fractionating the cracked distillates into a low boiling and a high boiling fraction, mixing the high boiling fraction at a temperature below 5 F. with an admixture of liquid sulfur dioxide and propane, passing the resulting admixture into a settling zone to permit phase separation wherein the relatively high antiknock components together with a substantial portion of the liquid sulfur dioxide collect in the lower part of the settling zone and the relatively low antiknock components together with a substantial portion of the propane collect in the upper part of the settling zone, removing said phases from said zone, passing the phase removed from the upper part of the settling zone to a second mixing zone and adding thereto liquid sulfur dioxide, passing said admixture into a second settling zone and again permitting phase separation as in the first settling zone, recycling the phase in the lower part of the second settling zone to the first mixing zone, removing the upper phase from the second settling zone and passing it into a third mixing zone where it is mixed with liquid sulfur dioxide, passing the admixture from the third mixing zone into a third settling zone and again permitting phase separation as in the previous settling zones, removing the phase in the lower part of the third settling zone and recycling it to the second mixing zone, removing the upper phase from the third settling zone and heating it to remove the sulfur dioxide and propane from the low antiknock components, and heating the phase separated from the lower part of the first settling zone to remove the sulfur dioxide and propane from the hi h antiknock components.

4. In a counter-current solvent extraction system for separating cracked petroleum naphtha containing relatively high antiknock components and relatively low antiknock components into phases, respectively, which contain more of the relatively high antiknock components and more of the relatively low antiknock components than the original cracked naphtha, the steps comprising mixing the cracked naphtha, liquid sulfur dioxide and liquid propane in a mixing zone at a temperature below 5 F., passing the resulting admixture into a settling zone to permit phase separation wherein the relatively high antiknock components together with a substantial part of the liquid sulfur dioxide collect in the lower part of thesettliiig zone and the relatively low antiknock components together with a substantial portion of the propanecollect in the upper part of the settling zone, removing said phases from said zone, passing the upper phase into a second mixing zone and mixing it with liquid sulphur dioxide at a temperature below 5 F., passing the admixture into a second settling zone to permit phase separation as in the first settling zone, removing said phases from said second settling zone, recycling the lower phase to the first mixing zone, passing the upper phase to a third mixing zone and mixing it with liquid sulphur dioxide andliquid propane at a temperature below 5 F., passing the admixture into a third settling zone and permitting phase separation as in the first settling zone, removing said phases from said third settling zone, recycling the lower phase to the second mixing zone, heating the upper phase from the third settling zone to remove the sulfur dioxide and propane from the low antiknock components and heating the lower phase from the first settling zone to remove the sulfur dioxide and propane from the high antiknock components.

5. In the process of. separating petroleum naphtha containing detonating and anti-detonatthe molecule and having a boiling point at least 40 degrees F. below the initial boiling point of the said petroleum naphtha being extracted.

6. In the process of separating petroleum naphtha containing detonating and anti-detonating constituents into fractions which are respectively more detonating and more anti-detonating than the original naphtha, the step comprising extracting the naphtha with liquid sulphur dioxide at a temperature between 0 degrees F. and i0 125 degrees F. in the presence of liquid propane.

OGDEN FITZ SIMONS. WILLIAM HERBERT BAHLKE. 

